The heart of a computer is an assembly that is referred to as a magnetic disk drive. The magnetic disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm adjacent to a surface of the rotating magnetic disk and an actuator that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The read and write heads are directly located on a slider that has an air bearing surface (ABS). The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic impressions to and reading magnetic impressions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The write head includes a coil layer embedded in first, second and third insulation layers (insulation stack), the insulation stack being sandwiched between first and second pole piece layers. A gap is formed between the first and second pole piece layers by a gap layer at an air bearing surface (ABS) of the write head and the pole piece layers are connected at a back gap. Current conducted to the coil layer induces a magnetic flux in the pole pieces which causes a magnetic field to fringe out at a write gap at the ABS for the purpose of writing the aforementioned magnetic impressions in tracks on the moving media, such as in circular tracks on the aforementioned rotating disk.
In current read head designs a spin valve sensor, also referred to as a giant magnetoresistive (GMR) sensor, has been employed for sensing magnetic fields from the rotating magnetic disk. The sensor includes a nonmagnetic conductive layer, hereinafter referred to as a spacer layer, sandwiched between first and second ferromagnetic layers, hereinafter referred to as a pinned layer and a free layer. First and second leads are connected to the spin valve sensor for conducting a sense current therethrough. The magnetization of the pinned layer is pinned perpendicular to the air bearing surface (ABS) and the magnetic moment of the free layer is located parallel to the ABS, but free to rotate in response to external magnetic fields. The magnetization of the pinned layer is typically pinned by exchange coupling with an antiferromagnetic layer.
Ever increasing data density and size requirements for devices such as disk drives and other electronic devices push researchers to continually find new ways of patterning ever smaller features with ever greater resolution. Current patterning techniques, such as those used to construct read and write elements in a magnetic head or to construct other features and devices are reaching their physical size and resolution limitations. One of the best techniques currently available is electron beam lithography. Typically, electron beam resists used for high resolution patterning (such as PMMA, KRS, ZEP, etc) are spin coated into a very thin layer and exposed in the e-beam tools. The process used following exposure and development of exposed resist (or unexposed in the case of negative contrast resist) requires significant thickness of the resist itself. For example, both lift-off and etching processes require thicknesses in excess of 100 nm. Resist thickness then becomes a serious limitation in a process in which very small features (for example 10 nm in size) need to be constructed, using 100 nm thick resist masks. The resolution of patterning such thick resist masks suffers from problems such as resist wall collapse, focus depth and other lithographic challenges, as well as creating undesirable high aspect ratio topographical structures.
A problem encountered by the data recording industry is that bit sizes are reaching a point where the recorded bits are becoming unstable. In currently available media, each bit contains a certain desired number of grains, such as about 100 to 500 grains. These grains are about 7 nm in diameter or so. In order for a bit to be recorded to the media, it is necessary that a large number of those individual grains all switch together (ie. are magnetized left, right, up or down) to have an acceptable signal to noise ratio. That means that as the size of the bit decreases, the size of the grains must decrease as well. As the bit size shrinks, those grains will become so small the media can become demagnetized (switched randomly) just at room temperature. Therefore, it would be desirable to find a way of constructing a magnetic media that can robustly record very small bits of data.
Therefore, there is a strong felt need for a process that can accurately pattern very small structures with a very high resolution. Such a process would preferably be capable of accurately patterning structures having a size of less than 100 nm, preferably smaller. There is also a strongly felt need for a process or structure for overcoming the size limitations of a recording media, to allow very small bits of data to be robustly recorded on a magnetic media.